Electric motor power assisted steering systems are known for exerting assistance functions that support a driver of a motor vehicle. Steering torques to be applied by the driver may be reduced by way of an electric motor superimposing an assist torque. The steering torque applied by the driver can be reduced by an electric motor in the steering system that generates an assist torque itself and such reduces the steering torque that has to be applied by the driver. For active steering systems, the assist torque may depend upon vehicle states such as steering angle, steering rate, and vehicle speed.
A typical steering control unit on a vehicle has a steering torque sensor to sense an actual steering torque and a steering angle sensor to sense a steering angle, both of which are generally part of the steering column or the steering gear. The steering control unit imposes an assist torque in addition to a steering torque applied by the driver. Most active steering systems are capable of compensating for disturbances acting upon the wheels and steering column of the motor vehicle while the vehicle is in motion, i.e., pull-drift compensation. However, active steering systems that compensate for noise have not taken into account a braking event when determining and applying steering torque compensation.
There is a need for a steering torque compensation system and method that provides a steering torque compensation in a steering control unit during a vehicle braking event.